Electric oven



March 31, 1936.

H. W. SCHULZE ELECTRIC OVEN Filed Aug. 11, 1934 I 7 I I I 22 24 I I I I I I I A J I I PREHEAT q H] I I Fig.3). I I

I I I I H I I I I l I I I I I I FIg l.

BRUIL l Inventor":

Herman W. SchuIze,

b5 l I i jA ctcfne Ij Patented Mar. 31, 1936 UNITED STATES PATENT OFFICE ELECTRIC OVEN Herman W. Schulze, Elmwood Park, Ill., assignor to Edison General Electric Appliance Company, Chicago, 111., a corporation of New York Application August 11, 1934, Serial No. 739,451.

3 Claims.

have been provided with two heating elements,

one in the lower portion of the oven arranged to maintain a normal or baking temperature, and a 15 second in the upper portion of the oven provided for broiling purposes, and further, both elements being arranged tobe connected in parallel for preheating the oven. The upper element only is used for broiling purposes.

20 It is desirable that the total wattage input to the two elements be restricted to as low a value as possible to accomplish the desired cooking results. An increase in connected load of the oven results in, higherwiring cost, poorer load 25 factor and greater hazard of overheating. In view of the fact that the capacity of the lower element must be sufiiciently large to maintain a baking temperature in theoven, and it is desirable that the total connected load be restrict- 30 ed as mentioned above, the wattage input of the broiling element necessarily is limited, generally to substantially the same heat generating capac-.

ity as the lower element for the usual or the ordinary sized baking or broiling oven. The wattage 35 inputto the broiling element is, therefore, some In accordance with this invention, the oven is provided with three heating elements, the capacity of any two of the elements substantially equal- 50 ing the total desirable load of the oven. One of these elements is positioned in the lower portion of the oven and has a heating capacity suflicient 'to maintain a baking temperature, while the remaining two elements are positioned in the upper portion of the oven for the purpose of eflfecting broiling operations. In order to rapidly preheat the oven, the lower unit is connected in parallel with one of the upper units, while the lower unit only is connected to the supply source in order to maintain a baking temperature. When it is desired to broil, the two upper elements are connected in parallel to the supply source. By reason of this arrangement a relatively high concentration, of heat required for eflicient broiling is obtained without increasing the connected load of the 'oven.

' For a more complete understanding of this in- -vention,.reference should be had to the accompanying drawing in which Fig. 1 is a diagrammatic view of an electric oven embodying this invention; and Figs. 2, 3, and 4 are diagrammatic views showing the various electrical connections for the heating elements provided for the oven of Fig. 1."

Referring to the drawing, this invention has been shown in one form as applied to an electric oven ill, the oven having any well-known form and shape, such for example as those provided on electric ranges for broiling and baking.

In one form of this invention, the oven is pro- 5 vided with an electric heating unit ll arranged in the lower portion of the oven, and two electric heating units [-2 and I3 arranged in the upper portion of the oven. These latter units are located so as to effect a broiling action on 'edibles properly placed within the oven. The lower heating element II is located within the oven in such position, and has a heat generating capacity suincient to maintain a normal or baking temperature within theoven.

The heating elements ll, l2, and I3, as shown, are of the sheathed type, such as described and claimed in the United States Patent to C. C. Abbott No. 1,367,341, dated February 1, 1921. Brief- 1y each element comprises a helical resistance 40 heating element II which is encased by a metallic sheath l5 and which is embedded in and sup ported in spaced relation with reference to-the sheath by means of a suitable heat refractory electrically insulating material "5, such as powdered magnesium oxide. It is to be understood, however, that theseheating elements need not be of the sheathed type, but may be or the wellknown open coil resistor type, or other suitable type. 60

The heating elements are provided with a suit-- able source of electrical supply I1.

As pointed out above, the heat generating capacity of the lower element H is such that it will maintain a suitable baking'temperature within the oven. This temperature is usually determined by the setting of a suitable temperature control device for the oven (not shown). For the baking and broiling oven of usual size, the element H 5 will have a capacity of approximately 1500 watts. In order to ra' idly-preheat the oven, it is con 'templated that the heating element II will be connected in parallel with one of the upper heating elements, such as the element l2, to apply a distributed heat to the upper and lower portions of the oven; and that their combined capacities will be suflicient to rapidly preheat the oven to the baking temperature. In the specific form of this invention shown, the upper heating element l2 has substantially the same heat'generating capacity as has the lower element II, that is, a capacity of approximately 1500 watts. It is further contemplated that the remaining upper heating element l3 will have such a capacity that when it is connected in parallel with the other upper heating element l2, the two elements will provide the relatively high concentration of heat tin the upper portion of the oven required for efficient broiling. In the specific form of the invention illustrated, the element l3 also has a heat generating capacity of 1500 watts.

The sizes of the heating elements will,.of course, vary with the size and character of the oven, but for a well insulated broiling and baking oven of the normal size it is contemplated that the lower heating element II will have a heat generating capacity of approximately 1500 watts, and that each of the elements l2 and I 3 in the upper portion of the oven will have a similar capacity.

It will be observed in the specific form of the invention illustrated that when the lower element H is connected to the supply source I! for baking, the total connected load of the oven will be 1500 watts, and that when this element is con- 0 nected in parallel with the upper element l2 forquick preheating to the baking temperature, the total connected load on the oven willbe 3000 watts. Furthermore, it will be observed that the relatively high wattage input for broiling will be obtained by connecting the two heating elements l2 and I3 in parallel and will be efiected without increasing the total load that is imposed upon the oven during the preheat period. That is, the total broiling load will be 3000 watts.

In broiling ovens heretofore generally used wherein only one upper heating unit is provided, the wattage input to the broiling element necessarily is considerably lower than that obtained in this invention, because the wattage input 55 available is considerably less than that which is available in this invention. It is to be noted that if the single upper heating unit of the previous broiling and baking ovens was made sufliciently large in wattage input to accomplishthe same 60 heat concentration for efiicient broiling as in this invention, then when it is connected in parallel with the lower heating element for quick preheating, the load imposed on the supply system will be materially in excess of 3000 watts.

' 75 is connected with the switch l8 by means of a The heating elements are controlled by means conductor l9, while the right hand terminal is a connected with the switch by means of conductors 20 and 2|. The left hand terminal of the upper heating element I2 is electrically connected to the switch by means of a conductor 22 and the right'hand terminal is electrically connected to the switch by means of a conductor 23 and the conductor 2|. of the upper heating element I3 is connected with the switch by means of a conductor 24, while its right hand terminal is connected with the switch by means of the conductors 23 and 2|.

Referring to Figs. 1-4 inclusive, it will be observed that when the switch I8 is in-"its, Oif' position,'all of the elements I I, l2, [3 are deenergized. In order to preheat the oven rapidly to v a baking temperature, such as 400 F. for example, the switch is moved to its controling position shown in Fig. 2-the Preheat position of the switch. In this position of the switch, it will be observed that the heating unit II will be connected to the two conductors of the electrical supply source l1, and that the upper heating element l2 will be connected to the supply source in parallel with the lower heating element l I. In this position of the switch, therefore, the energy input of three thousand watts will be applied to the upper and lower portions of the oven for quick preheating. When the oven has been heate'd substantially to its baking temperature of 400 F. for example, the switch will be operated to its Bake positionshown in Fig. 3, wherein the lower heating element ll alone will be connected to the supply source 11. This operation of the switch cuts down the wattage input to 1500watts which is applied to the lower portion of the oven for maintaining the baking or normal temperature. If it be desired to broil, the switch is thrown to its Broil position shown in Fig. 4 wherein the two upper heating elements l2 and I3 are electrically connected in parallel to the supply source II. The energy input to the upper portion of the oven is, therefore, 3000 watts; This will provide the necessary high temperature at the upper element for eflicient broiling.

It will be observed that this invention provides a very simple and eflicient control for an electric baking and broiling oven wherein the total load is limited, and yet, wherein a high temperature broiling unit is provided in the upper portion of the oven, the wattage input for broiling being materially in excess of that of the baking and broiling ovens heretofore generally used. Furthermore, it will be observed that the heating elements are arranged and controlled for rapid preheating, while one element alone is controlled for maintaining the baking or normal operating temperature.

The left hand terminal I While I have shown a particular embodiment J of my invention, it will be understood, of course,

that I do not wish to be limited thereto since many modifications maybe made, and I, theree fore, contemplate by the. appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an electrically heated oven, a source of electrical supply for said oven, a pair of electric heating elements in the upper portion of said oven having a combined heat generating capacity to maintain a broiling temperature in the upper portion of said oven and a single heating element in the lower portion of said oven having a heat generating capacity to maintain a desired baking temperature in said oven, the combined capacities of any two of said heating elements substantially equaling the total'energy load of said oven? imposed on said electrical supply source and switching means for connecting simultaneously one of said upper and said lower ofsaidelements to said supply source in order to rapidly pre heat said oven, for connecting said lower element only to said supply source for maintaining a baking temperature in said oven and for connecting both of said upper elements simultaneously to said supply source while said lower element is deener-' gized, to maintain a broiling temperature in the upper portion .of said oven, the said switching means thereby connecting said heating elements to said supply source for preheating, bakingand broiling so that the total energy load or said oven is never greater than the combined capacities of any two of said heating elements. A V 2. In an electrically heated-oven, an electrical supply "sourcewfor said oven, aheating element in the lower portion of sald'oven having a-heat generating capacity to maintains dw'ired 'baki'ng temperature in said oven, a second heating element in the upper portion of said ovenhaving a heat generating capacity substantially equal to the heat generating capacity of said first heating element and when connected in parallel with it, said elements together will preheat said oven rapidly to its baking temperature, a third heating element in said upper portion having a heat gencrating capacity substantially equal to the heat generating capacity of each of said first and sec- ,ond elements and such that whenconnecte'd in:

parallel with said second heating element; thetwo heating elements; together will maintain a desired broiling temperature in the upper portion of said oven, the combined capacities of any two of said heating elements substantially equaling the total load of said oven imposed on said electrical supply source, switching means for said heating elements, and'electrical connections between said heating elements, said means and'said electrical supply som-ce arranged the said switching means thereby connecting said heating elements to said supply source. for preheating, baking and broiling so that the total energy load otsaid oven is never greater than the combined capacities of two oi. said heating elements.

electrical supply for said oven, a heating element in the lower portion of said oven having a heat generating capacity sufficient to maintain a baking temperature in said oven, second and third heating elements each having substantially the same heat generating capacity as said first heating element located in the upper portion of said l5 3. In an electrically heated oven, a source 0! oven, the combined heat generating capacity oi' said second andthird elements being suflicient to maintain a broiling temperature in the upper portion of said oven and the combined capacities of any two of said heating elements substantially equaling the total energy load of said oven imposedonsaid electrical supply source, and a single multi-iposition switch for controllingsaid heating elements arranged in'one position to electrically' connect only said lower and one of said upper elements in parallel to said supply source for rapidly preheating said oven, in another posi- -t'ioh to connect said lower element only to said supply sourceior maintaining a baking temperature in said'oven and in still another position to connect only both of said two upper elements in parallel to said supply source for maintaining 'a broiling temperature in the upper portion or said oven.

HERMAN w. semmzn. 

